Control apparatus



Dec. 23, 1958 R. N. BOOTH 2,866,023

CONTROL APPARATUS Filed Nov. 5, 1956 INVENTOR. RUSSELL N. BOOTH ATTDRAEY United States Patent I CONTROL APPARATUS Russell N. Booth, Lakeville, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application November 5, 1956, Serial No. 620,242 9 Claims. (Cl. ZOO-61.06)

The present invention is concerned with a moisture responsive control device, in particular one which has a thin ribbon moisture responsive element.

In moisture responsive control devices the use of hair elements and other expensive elements has been quite common in the past, and this increases the cost of the overall control device. With the increase in residential air conditioning and residential dehumidification units there is a need for a relatively accurate and yet inexpensive moisture responsive control device for such application. is used for obtaining motion upon a change in the moisture content of the surrounding air to operate a control switch. The element is a material chemically known as a condensation product of a dibasic acid with a difunctional primary amine. desirable characteristics for use in a moisture responsive element.

It has negligible hysteresis when operating under a constant tension, it has practically a linear change in length through the humidity range for most applications, and it provides a large movement for small changes in the amount of water absorbed. In order to obtain successful operation of a device using the above material for the sensing element it is necessary to maintain a relatively uniform tension, less than some predetermined value, on the element. The present invention has a novel linkage to maintain a constant tension on the sensing element.

It is therefore an object of the present invention to provide an improved moisture responsive control device.

Another object of the present invention is to provide in an improved control device a means of maintaining a constant tension on a sensing element.

And still another object of the present invention is to provide an improved control device with a thin ribbon sensing element.

These and other objects will become apparent upon the study of the following specification and claims of which:

portion of the cover cut away.-

Figure 2 is a showing of one end of the sensing element with a clamp for holding the element.

Figure 3 is a front view of the control device showing the switch and the operating linkage connected to the sensing element.

Figure 4 is a view of a modified embodiment looking upward at the bottom of the linkage of a control device similar to that shown in Figure 1.

Figure 5 is a front view of a third embodiment of the control device showing only one lever which has a biasing spring for holding it against the switch.

Referring to Figure 1, a control apparatus is shown having a base or frame having a snap switch 11 mountedthereon. The switch is a conventional type having an operating plunger 12. Upon moving plunger 12 inward the switch is operated'to close the circuits between terminals 13 and 14. A sensing'element 15 is In the present invention a thin ribbon element This material has many Figure 1 is a front view of the control device with a includes the ears 32 and 33, is coated with a rubber-likei 2,866,023 Patented Dec. 23, 1958 is attached to a manual adjustment having a lever 22- which is attached at one end 23 to the frame. The other end of lever 22 is attached to clamp 20 by the insertion of a projection on the lever into a hole of the clamp. This is shown in greater detail in Figure 2 in which hole 24 in clamp 20 is shown having the projection therein.

Lever 22 is forced downward against its own spring resilience by a screw 25 which is attached to a control point adjusting knob 30. Upon adjustment of the knobthe normally fixed position of the upper extremity of element 15 is changed.

The lower extremity of element 15, which is also attached to a clamp 21, is connected to one extremity of an ambient temperature compensation bimetal 31 by.

means of a projection thereon being received into a hole of clamp 21. The clamps are held rigid on the associated projections by a cement, not shown. Clamps 20 and 21 are substantially the same; thus the description of clamp 20 as shown in Figure 2 describes both; clamps. Referring to Figure 2, the clamp has a pair of ears 32 and 33 opposite one another on the outer sides of the clamp. One side 34 of the clamp, which also material before assembly. Upon placing element 15 in the clamp and bending ears 32 and 33 downward to; pinch theelement between the main portion of the clamp .and the ears, as shown in Figure 2,. no part of the clamp including the ears will come in contact with the element. Such a coating not only aids the clamp in holding the smooth thin element 15 but also provides a protective Y coating should the ears 32 and 33 be pinched too hard against the element.

Referring to Figure 1, a bracket 51 is mounted on switch 11 by a pair of screws 36 and 37 received by frame 10 to hold the bracket and switch. The bracket has a downwardly extending portion 38, shown in Figure 4. A shaft 35 is mounted between the main part of the bracket and portion 38. Pivotally mounted on shaft 35 is a lever 40. Attached as a part of lever 40 is bimetal 31, the lever and bimetal of shaft 35. A portion 42 of lever 40 has a projection 43 thereon engaging a portion 45 of a second lever 44 also pivoted on shaft 35. Portion 45 is interposed beshown in Figures 1 and 3 other than to transmit movement from lever 40 to the plunger 12.

A spring 50 is attached to the outer extremity of lever 40 and bracket 51. The spring applies a clockwise force to lever 40 at approximately a 50 degree angle. Element 15 is attached to the outer extremity of bimetal 31 to apply a counterclockwise force to lever 40 at approximately 40 degrees. The aforementioned linkage is designed so that upon element 15 shortening to pivot lever 40 counterclockwise thereby lengthening its effective lever arm, the effective lever arm upon which spring 50 acts is shortened. The spring force increases as it is stretched, but by the present design of the linkage, it is possible to maintain a relatively constant tension on elepivoting as an integral part some other control device having zero loading, the tension maintained on the element is substantially constant throughout its range of movement.

Assuming for explanation purposes, switch .11 has an operating force requirement of 230 grams and a release force of 200 grams. It is obvious that. as lever=40f moves clockwise, upon the expansion of element-lsftoen'gage plunger 12 through lever 44, a portion of the force of. spring 50 is used to depress plunger 12'. Thusfas'plung er" control device requiring little or noload such as a poten-' tiometer the force of spring 50 would always be available to keep a constant tension'on element 15. Throughout the operating range of the element, where no loading is required on'control device 11, the linkage provides a zero rate spring bias on the element.

A second embodiment is identical to that described above except, as shown in Figure 4, lever 40 is biased in a clockwise direction as seen in Figure 1, by spring 50 attached between the outer extremity of lever 40 and bracket 51, and a constant bias isplaced on plunger 12 of the switch-by spring 52 acting on lever 44. The additional force applied'through lever 40 when the element 15 expands or contracts is used to operate the switch. Assumingthe same operating and release force requirements of 230 and 200 grams, respectively for switch 11 the Mason plunger 12 provided by lever 44 might be adjusted to less than 200 grams. The force needed to operate the switch as supplied by element 15 through lever40 is'the'n 30 grams. The lever arm ratio between pivot 35 and plunger 12 and pivot 35 and element 15 is. approximately lto 2% when lever 40'isnearthe It is'seen that'the variation in the tension on the element throughout the range of the. switch is reduced to approximately" 12 grams."

operating position of: switch 11.

Therefore even with aficontrol device requiringa rela-' tively large force for operation it is possible to maintain the. variation in element tension through its operating range rather low.

In Figure another embodiment is. shown. This em-- bodiment is similar to that shown in Figure 1, except that lever 44' is. omitted. and. actsv directly on plunger-12. The force to operate the switch 11 by pushing plunger 12 inward is obtained through spring 50 as it pivots. lever 40 clockwise about pivot 35 when element expands upon taking on moisture. The bimetal 31 is also. shown aslpart of the assembly of lever 40.

In Figure 1, as mentioned heretofore, lever 44 is not being used, thus the operation of the embodiments: of:.

Figures 1. and 5 are similar. Whena switch is used.

which. requires: a. low or Zero release forcetheseembodimentsareusedas element. 15 uponshortening and acting. through. lever 40. can remove all the load: onaplungera 12.

asproduced by spring 50. The. embodiment in Figure 1 is substantially. as the invention isv presentlyproduced and it can be easily modified toprovide; a constant switch.

load by placing: spring 52- on lever 44.

In all three embodiments of the present invention.

shown in Figures. 1, 4, andS; themaximum tensionon= the element can be preselected by spring 50; This, is; importantas thetensile. strength of elementssnch as.15-' islow. Should knob. 3.0 be turned from. a low-to high setting the upper. end of.. element 15 would be raised;

however the tension, on element. 15 will not exceed the.

predetermined maximum value. as lever 40 would only lift away from. plunger 12.

The device has a cover 6.01 as shown in Figure. 1 which.

fits, frame 10. In order to prevent thecover from touchingterminals 13 and; 1.4: a'paper insulator. 61- is; placed over. these terminalsand heldon switch 1:1;f b'=' screws. 36;and 37. The. terminals. 13 and 114: ar.ei..c.on-.) meted-through conductors 62: andtfifittoiamoisture conna aasaa dition changing device which might be humidification or dehumidification apparatus to add moisture or take out Operation.

For explanation purposes let us'assume. that the device as shown in Figure 1 is attached to a dehumidification moisture condition changing device so that upon an increase in the moisture content of. the air surrounding element 15 will expand to cause button 12 to move inward and. completeithecircuitbetween terminals 13 and 14. This will energize the dehumidification apparatus and begin to remove the water from the air.

Neglecting the force required on plunger 12 to operate switch 11, the tension on element 15 provided by the spring 5.0. remains substantiallyconstantthroughout the range of-change inlength of the element. This effective zero rate spring bias on the element is'quite important. as; thin ribbon elements of thetype used have little hysteresis when the tension on the element is constant. As the, elementexpands-and the lever 40. engages plunger 12- a portion of theforce developed by spring 50 is then. applied to; the, plunger and depending upon the needed force to operate the switch the tension on theelementis: decreased. Withthis novel zero rate. spring mechanism it- .is; seen that at: no. time will the tension on the element exceed. some predetermined maximum value. This would. ev n b th eas p n a j s m o c n r l:- poi nt adjusting: knob 30 to a higher. humidity level as. IGVQBAQ- would. only movecounterclockwise away fromtheplunger and the tension on the element would remain th e -.same,.

A constantloading; on, plunger 12 might be provided through lever 44; by aspr ing 52 as shown in Figure 4.

This constant, loading could be selected to be slightlybelow the; release, force, necessary for. theparticular switch.

used'p With the constant loading onthe switch plunger the force to be supplied by lever 40- need only be the dif{ ferenee in; force. between the release and. operating forces; of t s h. n e ssum val es pa a switch, this is. .30 grams. As the lever moves back and. forth to operate the, switch the tension on: element 15.va-ries.-:

approximately 12 grams which would be quite low.

The. embodiments shown in Figures 1,. 4,, and 5 operate substantially the same except. where the constant. loading; is. desired.- the. aforementioned; spring.- 52 can;v be placed: on. leverv 44. as shownin the embodiment of Fig-, ure 4.

As; the temperature. has; somev effect on the elementlS the bimetal 31 acts to compensate for; this temperatureeffect so that should the element expand on a temperature change the extremity-of bimetalSL conpected to clamp ld-m ve ownwar ov ake o th nc e ene a- The bimgeta' l 1 In a moisture responsive. device, a. frame, a lever.

pivotally mounted on said frame,. control; means, said leven means being adapted to-operate-saidcontrolmeans when pivotedin: a first direction, .a. spring connected to... saidframe andsaiddever; theforce applied by the sp ring.;, to said leve-nheing at. substantiallya; .5 Qtdegree anglezand 1 biasing;'said rleverrin .saidnfinst; dir.ecti' c m;, v and a thin;

oa-mo st pg ve lementliansins. n. ens hupw a change in the moisture level therearound, said element being made of a condensation product of a dibasic acid with a difunctional primary amine, means connecting said element between said base and said lever, the force applied by said element to said lever being at substantially a 40 degree angle, said first mentioned and said last mentioned forces being substantially normal to each other so that upon a change in the length of said element to rotate said lever the force applied to said element remains constant.

2. In an atmospheric moisture sensing device, a frame,

a control element carried by said frame, a lever pivoted in said frame and adapted to actuate said control element, astrc'tchable humidity responsive element acting between said-frame and said lever on a line making an acute angle with said lever and so disposed that the angle increases to increase the effective length of said lever as said element contracts, and a spring acting between said frame and said lever on a line making an acute angle with said lever and so disposed that said last mentioned angle decreases as said element contracts.

3. In an atmospheric moisture sensing device, a frame, a control element carried by said frame, a lever pivoted in said frame andadapted toactuatesaid control element, a stretchable humidity responsiveelement acting between said frame and said. leverfanda'spring acting between said frame and said, ieverien ai'line making an acute angle with said lever and'so disposed that said last mentioned ang e decreases as said'element contracts to maintain a constant loa'donsaid element.

4. In an atmosphericmoisture sensing device, a frame, a control element carriedby said frame, said control element requiring a force'of ,a'predetermined value to operate said element'a'nd apredetermined lesser force to release said element from its operated position, a first lever pivoted on said frame and adapted to place a force on said control element less than said release force, a second lever pivoted on said frame and adapted to actuate said control element by applying an additional force so that said force of said first lever and said second lever exceeds said operating force, a humidity responsive element acting between said frame and said second lever, and a spring acting between said frame and said second lever on a line making an acute angle with said second lever and so disposed that said angle decreases as said element contracts upon a change in atmospheric moisture.

5. In a moisture control device, a base member, a sensing element having an overall length which varies with moisture content in the surrounding space, an adjustable mounting member to which one extremity of said sensing element"isconnecte'd, a lever pivoted about a shaft on said base, ,a' switch'having an operating plunger, a portion of said lever engaging said plunger, an outer extremity of said leverhaving a second extremity of said sensing element connected thereto, a spring, means connecting said spring between said outer extremity of said lever and said base so that said spring applies a force to said lever at an angle to the force of said sensing element thereby upon said sensing element lengthening upon a change in the moisture level said lever pivots to operate said switch- 6. In a humidity control device, a base member, a thin ribbon sensing element attached at one extremity to said base member, said element changing in length as the moisture content of the air therearound changes, a shaft mounted to said base member, a first member pivotally mounted on said shaft, a snap switch having an operating plunger, said switch being mounted on said base member, said first member having a portion engaging said plunger, first resilient means attached between said member and said base member for applying a biasing force to said first member and against said plunger, a second member pivotally mounted on said shaft, said member having a portion engaging said first member, means connecting the other extremity of said element to said second member, second resilient means connected between said second member and said base member for applying a tension force on said element, said second resilient means being connected so that as said second member pivots the tension force on said element will remain constant.

7. In a moisture responsive device, a thin ribbon sensing element, a base member, switch means, a member pivotally mounted on said base member and adapted to operate said switch means upon a predetermined movement of said member, connection means for connecting one extremity of said element to said member and the other extremity to said base member, said connection means comprising a clamp coated with a soft material so that upon clamping said element said clamp does not come in direct contact with said element.

8. In a moisture responsive device, a sensing element made of a relative thin ribbon of material, switch means having an operating member, a base member, connecting means connecting said sensing element between said operating member and said base member, said connecting means comprising a clamp having one surface covered with a protective coating so that when said clamp is placed on said sensing element said coating will protect said element and provide a better hold onsaid element.

9. In an atmospheric moisture sensing device, a frame, a control element carried by said frame, a lever pivoted in said frame and adapted to actuate said control element, said lever having a portion made of temperature responsive bimetal, a humidity responsive element acting between said frame and said bimetal, and a spring acting between said frame and said lever on a line making an acute angle with said lever and so disposed that said last mentioned angle decreases as said element changes in length with a change in atmospheric moisture.

References Cited in the file of this patent UNITED STATES PATENTS 1,319,055 Eggleston Oct. 21, 1919 1,919,446 Mills et a1. July 25, 1933 1,926,706 Eggleston et al. Sept. 12, 1933 2,191,630 Shutts Feb. 27, 1940 2,262,342 Shaw Nov. 11, 1941 2,503,273 Johnson Apr. 11, 1950 2,694,757 Nickells Nov. 16, 1954 

